The present invention relates to an oil lubricated vacuum pump and, in particular, to an oil separator for this type of pump.
British Pat. No. 912,119 discloses an oil lubricated vacuum pump employing a valve-type oil separator disposed adjacent the suction opening of the pump and adapted for coupling to a vacuum line. The separator comprises a spherical or ball element which is pressed against a valve seat of the separator by a helical spring. The ball, valve seat and helical spring are arranged and dimensioned so that the stream of air sucked out of the vacuum line can pass into the vacuum pump whereas oil ejected toward the suction opening by the vacuum pump during operation is prevented from entering the vacuum line.
The results obtained with such prior art vacuum pumps are not completely satisfactory because it is difficult to make the ball valve-valve seat interface sufficiently tight and, after sustained periods of operation, enough oil enters the vacuum line to adversely influence the operation of the connected vacuum boosters and other equipment.
A satisfactory design of such prior art ball valve oil separators is realizable only with difficulty because two contradictory requirements must be met. On the one hand, the valve element should be pressed onto the valve seat with a comparatively large spring force to produce the desired tightness and reliably prevent the valve element from lifting off the seat when the acceleration surges generated by the vacuum pump are large. On the other hand, the valve element should be pressed into the valve seat with as little spring force as possible to permit the stream of air sucked in by the vacuum pump to pass with as little loss as possible since any intermediate biased valve represents a loss of attainable vacuum. The comparatively large masses of the known valve-type oil separators used in prior art vacuum pumps make satisfactory dimensioning of these prior art oil separators particularly difficult.
It is an object of the present invention to provide an oil separator for an oil lubricated vacuum pump which prevents the entrance of oil into the vacuum line under all conceivable operating conditions, including large acceleration surges, without there being any noticeable reduction in utilizable vacuum pressure.